Airlines have a recipe to reach zero emissions by 2050. The key ingredient: cooking oil

  • On Dec. 1, 2021, this United Airlines 737 Max 8 became the first commercial airliner to use biofuel as the sole fuel for one of its engines. (United Airlines/TNS)

Earlier this month, a United Airlines flight from Chicago to Washington made a bit of aviation history, completing a 600-mile trip that the airline hopes will prove the first leg of a journey to a greener future.